Herpes simplex (HSV-1 and HSV-2): IgG, IgM and PCR

Do you have blisters or sores around the lips or genitals, or want to know whether you carry herpes virus? Herpes simplex tests show whether it is herpes, which virus type is involved and whether you were infected before. Swab PCR detects virus in the lesion itself, while blood antibodies indicate previous infection.

Who is this test for

• people with genital or oral blisters or sores when a doctor wants to confirm herpes and identify its type;
• people with recurrent genital lesions without a confirmed diagnosis;
• partners of people with genital herpes wanting to know whether they are already infected;
• pregnant women and women planning pregnancy if they or their partner have genital herpes, at a gynaecologist’s discretion;
• people being checked for sexually transmitted infections.

If a newborn in the first weeks of life has fever or blisters, feeds poorly or is unusually sleepy, or an adult develops confusion or seizures with fever, call emergency services immediately (194 or 112).

What the test reveals

There are two virus types. HSV-1 most often causes cold sores, but increasingly also genital herpes. HSV-2 almost always causes genital herpes. After the initial infection, the virus remains dormant in nerve cells for life and can recur occasionally.

• HSV PCR detection detects virus in the sample and identifies HSV-1 or HSV-2. It is the most reliable test when lesions are present.
• HSV-1 IgG and HSV-2 IgG show whether you have ever been infected with a particular type, but not when or where on the body.
• HSV-1 and HSV-2 IgM are less reliable: they also appear during recurrences and do not distinguish virus types.

The test and preparation

Antibodies require venous blood without special preparation. For PCR with a visible lesion, the best sample is a swab from a blister or fresh sore taken in the first days before it dries. Swab collection takes a few minutes.

Within STI testing, samples are the same as for other PCR tests: women provide a vaginal swab, which they can self-collect at home with a kit, or first-catch urine; men provide first-catch urine or a genital swab. Bring urine, ideally the first morning urine or after at least two hours without urinating, as soon as possible, preferably within 2 hours.

What your results mean

• PCR positive: herpes simplex virus was detected in the sample, and the report identifies the type. This helps assess recurrence likelihood: genital herpes caused by HSV-2 recurs more often.
• PCR negative: the virus was not detected. If a swab was taken from a healing lesion, the result may be falsely negative.
• IgG positive: infection with that virus type occurred previously, perhaps long ago. Most adults have HSV-1 IgG. Weakly positive HSV-2 IgG may be falsely positive, so a doctor sometimes checks it using another method.
• IgG negative: there has been no infection or it is too early, because antibodies may take around three months to develop.
• IgM: a positive result does not prove recent infection, and a negative result does not exclude it.

A doctor interprets the result alongside the appearance of lesions and your symptoms.

How to arrange testing

You can attend blood collection and swab sampling without an appointment or referral at one of our branches throughout Croatia (listed on the Contact). A nurse takes the swab; urine or a swab collected at home may be submitted at any branch. Prices for all tests and panels are listed in the price list. If you want checks for several sexually transmitted infections at once, see sexually transmitted infection testing, or during pregnancy the TORCH test.

Frequently asked questions

What is the difference between HSV-1 and HSV-2?

Both types can cause oral and genital lesions. HSV-1 is more common on the lips, and genital herpes caused by it recurs less often. HSV-2 almost always causes genital herpes and recurs more frequently.

Can I have herpes without knowing?

Yes. Many infected people never have visible lesions or mistake them for a scratch or irritation, yet still shed virus occasionally and can transmit it.

When should I test after a risky contact?

If lesions appear, have a PCR swab as soon as possible. Without lesions, checking antibodies becomes useful only around three months after contact, because they may not have formed earlier.

Should I test if I have no symptoms?

Routine testing without symptoms is generally not recommended. It is useful for partners of someone with genital herpes, in pregnancy at a gynaecologist’s discretion, and during STI checks.